Question

compare the somatic nervous system to the autonomic nervous system in these areas: control center locations, effectors, neurotransmitters, pathways, type of effect (positive or negative), responses. explain the role of varicosities in the autonomic nervous system. explain the differences in location and origins of each branch of the ans. explain what dual innervation is and describe its importance. explain what dynamic antagonism is and describe its importance. list examples of organs that do not have dual innervation and describe the effects of the sympathetic division on each of these organs. compare the lengths of the preganglionic and postganglionic neurons in both branches of the ans and relate this to the location of the ganglia of each branch. compare the differences in function between the two branches of the ans. identify scenarios in when each branch of the ans is activated. describe the effects of the parasympathetic and sympathetic divisions on the following organs: heart, blood vessels, gastrointestinal tract, lungs, adrenal medulla, and external genitalia.

Answer 1

The somatic nervous system controls voluntary muscle movements, while the autonomic nervous system regulates involuntary functions of organs. The ANS is divided into sympathetic and parasympathetic branches, which have contrasting effects on the body. Dual innervation allows both systems to modulate organ function, and dynamic antagonism maintains homeostasis.

Step-by-step explanation:

Comparison of Somatic and Autonomic Nervous Systems

The somatic nervous system (SNS) controls voluntary movements and involves skeletal muscles. Its control centers are primarily in the cerebral cortex, allowing conscious control over skeletal muscles. The main neurotransmitter is acetylcholine, which directly activates muscles through neuromuscular junctions.

In contrast, the autonomic nervous system (ANS) regulates involuntary functions targeting cardiac and smooth muscles, as well as glands. It has control centers located in the brainstem and spinal cord. The ANS uses neurotransmitters like acetylcholine and norepinephrine and operates through two-step pathways: preganglionic to ganglion, then postganglionic to the effector.

The role of varicosities in the ANS is to release neurotransmitters along the length of postganglionic fibers, allowing diffuse modulation of target tissues. The ANS is divided into sympathetic and parasympathetic branches, each originating from different regions: thoracolumbar for sympathetic and craniosacral for parasympathetic.

Dual innervation refers to most organs being regulated by both sympathetic and parasympathetic inputs, usually with opposite effects, thus providing a mechanism for fine control. Dynamic antagonism is the balance between these two divisions, important for maintaining homeostasis.

Some organs, like adrenal medulla, piloerector muscles, and sweat glands, do not receive dual innervation and are primarily influenced by sympathetic activation. The lengths of the preganglionic and postganglionic neurons vary, with the sympathetic division typically having short preganglionic and long postganglionic neurons, while the parasympathetic division has the opposite configuration.

Functions differ between these two branches, with sympathetic activation generally associated with 'fight or flight' responses, increasing heart rate and blood pressure, and parasympathetic activation associated with 'rest and digest' responses, promoting calm and energy conservation.

Effects on Organs by ANS Divisions

• Heart - Sympathetic increases rate; Parasympathetic decreases rate.
• Blood vessels - Sympathetic causes constriction; Parasympathetic has less influence.
• Gastrointestinal tract - Sympathetic inhibits activity; Parasympathetic stimulates activity.
• Lungs - Sympathetic dilates airways; Parasympathetic constricts airways.
• Adrenal medulla - Sympathetic stimulates hormone release; Parasympathetic has minimal effect.
• External genitalia - Sympathetic causes ejaculation; Parasympathetic causes erection.